provide a direct way to access node's id instead of from edge's _dst

[whitewum]

I know i can fetch destination nodes' id by so called _dst from the edge.
But it is indirect and a bit strange ( to get a node id from the edge).
It is better to be done by the optimizer than a new concept introduced to the user .

E.g. I prefer to get (v)id like this:

GO FROM $personId OVER person_isLocatedIn_place YIELD \
   id($$.place) AS place'vid  -- id() is cypher sytle

rather than

GO FROM $personId OVER person_isLocatedIn_place YIELD \
person_isLocatedIn_place._dst AS place'vid

[Amber1990Zhang]

One question here, how do you know that the in edge is pointed to the place type vertex? Do I have to DEXCRIBDE EDGE before the query if I'm not familiar with the schema?

[CPWstatic]

Please track it with #2594 .